Wet-spun Poly Research Articles

Additive Manufacturing of Wet-Spun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-Based Scaffolds Loaded with Hydroxyapatite.

Tissue engineering represents an advanced therapeutic approach for the treatment of bone tissue defects. Polyhydroxyalkanoates are a promising class of natural polymers in this context thanks to their biocompatibility, processing versatility, and mechanical properties. The aim of this study is the development by computer-aided wet-spinning of novel poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-based composite scaffolds for bone engineering. In particular, PHBV scaffolds are loaded with hydroxyapatite (HA), an osteoinductive ceramic, in order to tailor their biological activity and mechanical properties. PHBV blending with poly(lactide-co-glycolide) (PLGA) is also explored to increase the processing properties of the polymeric mixture used for composite scaffold fabrication. Different HA percentages, up to 15% wt., can be loaded into the PHBV or PHBV/PLGA scaffolds without compromising their interconnected porous architecture, as well as the polymer morphological and thermal properties, as demonstrated by scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. In addition, HA loading results in increased scaffold compressive stiffness to levels comparable to those of trabecular bone tissue, as well as in higher in vitro MC3T3-E1 cell viability and production of mineralized extracellular matrix, in comparison to what observed for unloaded scaffolds. The observed mechanical and biological properties suggest the suitability of the developed scaffolds for bone engineering.

Understanding the evolution of mechanical and electrical properties of wet-spun PEDOT:PSS fibers with increasing carbon nanotube loading

Unprecedented demands for advanced fiber materials have been raised by the quick development of wearable intelligent devices. It is still a significant problem to increase the mechanical qualities of fibers without compromising their chemical properties. The impact of different carbon nanotube (CNT) loading on the physical properties of wet-spun poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) fibers are explored in depth along with a wet spinning process for the continuous fabrication of PEDOT:PSS/CNT hybrid fibers. We discovered that the main challenge in a mechanically reinforced system of PEDOT:PSS fibers is to prevent the binding and aggregation of CNT within the fibres; enhancement is typically accomplished at 5 wt% CNT loadings. On the other hand, the conductivity of PEDOT:PSS fibers rises as CNT content increases. By applying the new understanding, the highly conductive PEDOT:PSS/CNT hybrid fiber exhibits greater rate performance and cycle stability in the electrochemical test is obtained. The PEDOT:PSS/CNT hybrid fiber-based fiber-shaped supercapacitors (FSC) have been assembled and they show good long-term cycle stability. Meanwhile, energy and power densities reach ∼16.05 mW h cm−3 and ∼13292 mW cm−3, respectively. This work provides a favorable reference for the mass production of fiber electrodes with high mechanical properties for energy storage.

Construction of hierarchical polypyrrole coated copper-catecholate grown on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) fibers for high-performance supercapacitors

Fiber-shaped supercapacitors (FSCs) are considered as the optimal candidate for wearable energy devices, due to their high safety, excellent electrochemical stability, workability and body adaptability. However, the specific capacitances of today’s FSCs such as carbon nanotube fibers and graphene fibers, are still not high enough for practical applications due to the limitation of their energy storage mode. So, we design a ternary composite fiber-shaped electrode: First, a kind of metal organic framework (MOF), copper-catecholate (Cu-CAT) nanorods, are in-situ grown on a wet-spun poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) fiber at the ambient temperature. Second, polypyrrole (PPy) is electrodeposited on the surface of the Cu-CAT/PEDOT:PSS fiber to obtain PPy@Cu-CAT@PEDOT:PSS fiber (PPy@Cu-CAT@PF). The growing Cu-CAT with high porosity anchored on the fiber surface provides electrochemical activate sites and the encapsulation of PPy effectively provides a continuous charge transfer path and improve its cycling stability. Notably, the PPy@Cu-CAT@PF electrode exhibits a satisfactory areal capacitance of 669.93 mF cm−2 at 2 mA cm−2, which remains 61.66% even at a high current density of 20 mA cm−2. Furthermore, the assembled symmetric FSC displays excellent electrochemical properties and outstanding mechanical flexibility, demonstrating its feasibility as a wearable supercapacitor.

Coordination and hydrogen bond-coadjusted highly stretchable wet-spun poly(acrylic acid) fiber and its stable activity as Fenton catalyst

High stretching is an effective route to attain high performance fiber. Therefore, the stretchability of wet-spun poly(acrylic acid) (PAA) fiber is important for the preparation of high performance PAA fiber by stretching. A combination of coordination and hydrogen bonding was synergistically used to prepare highly stretchable wet-spun PAA fibers, and high stretching was subsequently carried out to induce the production of molecular orientation and fibrillar crystals, which can remarkably enhance the strength of resulting fiber. The breaking strength of stretched fiber reached up to 1.631cN/dtex, increasing by 2813% compared to that of unstretched fiber. Moreover, high stretching was used to thin the resulting fiber and promote the transformation of PAA chains from coiled to extensional conformation, so that the carboxyl groups wrapped by coiled PAA chains were exposed to the environment. When the highly stretched fiber was used to decolorize methylene blue (MB) aqueous solution, the exposed carboxyl groups can quickly re-coordinate with the iron ions eluted by MB aqueous solution to minimize the loss of iron ions. The measurement results showed that the average concentration of eluted iron ions was only 3.20 mg/L during 40 operation cycles for the highly stretched fiber, decreasing by 64.0% compared to that of unstretched fiber. Due to low iron ion leaching-out, the highly stretched fiber showed superstable activity in catalyzing H2O2 to oxidatively decolorize MB. The research results revealed that the obtained fiber can decolorize more than 90% MB within 3 min during 40 cycles without showing any obvious attenuation in decolorization efficiency and decolorization rate. In this case, the Fenton catalysts reported by literature are scarcely comparable to the prepared fiber in many aspects. Therefore, the fiber prepared in this work can be expected to show great potential for application in the field of dye wastewater treatment.

An in vitro chondro-osteo-vascular triphasic model of the osteochondral complex

The generation of engineered models of the osteochondral complex to study its pathologies and develop possible treatments is hindered by the distinctly different properties of articular cartilage and subchondral bone, with the latter characterized by vascularization. In vitro models of the osteochondral complex have been mainly engineered as biphasic constructs containing just cartilage and bone cells, a condition very dissimilar from the in vivo environment. The different cellular components of the osteochondral complex are governed by interacting biochemical signaling; hence, to study the crosstalk among chondrocytes, osteoblasts, and endothelial cells, we have developed a novel triphasic model of the osteochondral tissue interface. Wet-spun poly(ε-caprolactone) (PCL) and PCL/hydroxyapatite (HA) scaffolds in combination with a methacrylated gelatin (gelMA) hydrogel were used as the polymeric backbone of the constructs. The scaffold components were engineered with human bone marrow derived mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells (HUVECs), and differentiated using a dual chamber microphysiological system (MPS) bioreactor that allows the simultaneous, separate flow of media of different compositions for induced differentiation of each compartment towards a cartilaginous or osseous lineage. Within the engineered Microphysiological Vascularized Osteochondral System, hMSCs showed spatially distinct chondrogenic and osteogenic markers in terms of histology and gene expression. HUVECs formed a stable capillary-like network in the engineered bone compartment and enhanced both chondrogenic and osteogenic differentiation of hMSCs, resulting in the generation of an in vitro system that mimics a vascularized osteochondral interface tissue.

Vancomycin Loaded Gelatin Microspheres Containing Wet Spun Poly(ε-caprolactone) Fibers and Films for Osteomyelitis Treatment

In this study, it was aimed to develop drug eluting biodegradable and biocompatible bone supportive fibers and films, which can locally be applicable on the infected bone defect area for osteomyelitis treatment. For this purpose, vancomycin (Vm) loaded gelatin (G) microspheres were prepared and dispersed into poly(e-caprolactone) (PCL) solution and then the suspension was processed as films and fibers by solvent casting and wet spinning techniques, respectively. The mean particle size distribution and morphology of Vm loaded G microspheres were characterized by laser diffraction method and scanning electron microscopy, respectively. In vitro Vm release profiles and release kinetics from microsphere, fiber and film formulations were investigated. In vitro biodegradation properties of fiber and film formulations were examined in both hydrolytic and enzymatic media during 25 days period. The cytotoxicity of Vm eluting films and fibers were tested on L929 cells by MTT assay. Presence of PCL in film and fiber formulations retarded the release of Vm from microspheres and provided long term sustained release. Vm eluting films and fibers exhibited strong antibacterial properties against Staphylococcus aureus and Staphylococcus epidermidis.

Study on the Flame Retardant and Mechanical Properties of Wet-spun Poly(acrylonitrile-co-vinylchloride) Fibers with Antimony Trioxide and Zinc Hydroxystannate

To produce flame resistant poly(acrylonitrile-co-vinyl chloride) (PANVC) fibers (limiting oxygen index (LOI)> 28%) for flame retardant work wear, PANVC solutions containing antimony trioxide (ATO) and zinc hydroxystannate (ZHS) flame retardants at various composition ratios were wet spun using laboratory-scale equipment. The amount of ATO and ZHS added was determined to be 15 phr using the thin material vertical burning test. The LOI values of PANVC increased considerably from 27.9% to 33.1% with increasing ZHS composition ratio, but no significant synergistic effects were observed between ATO and ZHS. With increasing ZHS composition ratio, more densified structures of the char layer were observed after combustion. ZHS was found to be a more effective and suitable flame retardant for PANVC than ATO. The PANVC fibers had a round cross section and the ATO and ZHS particles were distributed uniformly in the PANVC fibers. The presence of ATO and ZHS particles decreased the tenacities of the pure PANVC fibers slightly.

Wet-spun poly(ionic liquid)-graphene hybrid fibers for high performance all-solid-state flexible supercapacitors

Abstract It is crucial to develop flexible and wearable electronic devices that have attracted tremendous interest due to their merits on compactness, flexibility and high capacitive properties. Herein we report the continuously ordered macroscopic poly(ionic liquid)-graphene fibers by wet spinning method via liquid crystal assembly for supercapacitor application. The fabricated all-solid-state supercapacitors exhibited a high areal capacitance (268.2 mF cm−2) and volumetric capacitance (204.6 F cm−3) with an outstanding areal energy density (9.31 µWh cm−2) and volumetric energy density (8.28 mWh cm−3). The fiber supercapacitors demonstrated exceptional cycle life for straight electrodes of about 10,000 cycles (94.2% capacitance retention) and flexibility at different angles (0°, 45°, 90°, 180°) along with a good flexible cycling stability after 6000 cycles (92.7% capacitance retention). To date, such a novel poly (ionic liquid)-graphene fiber supercapacitors would be a new platform in real-time flexible electronics.

Wet-spun poly(ε-caprolactone) microfiber scaffolds for oriented growth and infiltration of smooth muscle cells

The tissue engineered blood vessel requires oriented fibrous scaffold as template to guide smooth muscle cells (SMCs) oriented growth and infiltration. It is a considerable challenge to fabricate this kind of fibrous scaffold. In this letter, we developed a new wet-spinning system that involves a blended solution of edible oil and hexane as a non-solvent coagulation bath to fabricate oriented poly(ε-caprolactone) (PCL) microfiber scaffold. The fiber diameter and porosity could be controlled in the range of 7 to 27μm and 68 to 82%, respectively. SMCs could grow in an oriented fashion along the fibers and infiltrate inside the scaffold as well as maintain SMCs phenotype. This oriented microfiber scaffold has a promising potential for regenerating blood vessels and other fibrous tissues such as tendon, ligament and intervertebral discs.

Simultaneous effects of polymer concentration, jet-stretching, and hot-drawing on microstructural development of wet-spun poly(acrylonitrile) fibers

Investigation of structural development of acrylic fibers during the early stages of the wet-spinning process has great importance both in carbon fiber and textile industries. The simultaneous effects of increasing polymer concentration, jet-stretching and hot-drawing on porosity, morphology, and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. The detailed microstructure of the voids was characterized by electron microscopy, porosimetry, and thermoporometry. The effects of jet-stretching/hot-drawing on the overall porosity of the fibers were negligible below a threshold polymer concentration. Increasing polymer concentration from 10 to 20 vol.% reduced the total porosity. Hot-drawing was more effective in reducing the overall porosity of the fibers in comparison with jet-stretching. Stretching and drawing replaced the macrovoids by dense ligaments but did not change the volume fraction of nanovoids, however, shifted nanovoids size distribution toward smaller values. In general, Young’s modulus and elongation at break increased by decreasing overall porosity, however, they depended also on the distribution of voids size and chain orientation along the fiber axis. Strength–diameter correlation showed a good agreement with the Griffith’s theory.

Exploring the effects of non-solvent concentration, jet-stretching and hot-drawing on microstructure formation of poly(acrylonitrile) fibers during wet-spinning

The simultaneous effects of non-solvent concentration in the spinning dope, jet-stretching and hot-drawing on porosity, morphology development and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. Addition of non-solvent to the spinning dope increased dope viscosity, the entanglement density of the polymeric solution and the number of entanglements per chain. Drawability of the as-spun fiber depended on the number of entanglements per polymer chain. Therefore, addition of non-solvent improved or spoiled drawability of the wet-spun fibers based on the concentration of the initial spinning dope. Hot-drawing and jet-stretching did not affect the fraction of nanovoids but shifted their size distribution towards smaller values. However, hot-drawing was more effective in reducing the overall porosity of the fibers in comparison with jet-stretching. Fiber tenacity increased when overall porosity decreased. Finally, strength-diameter correlation showed good agreement with the Griffith’s theory.

Micrometer-scaled OFET channel patterns fabricated by using PEDOT/PSS microfibers

We have easily fabricated channel patterns of organic field-effect transistors (OFETs), in which channel lengths were 5 μm, by using wet-spun poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) microfibers with diameters of ca. 5 μm. Pentacene-based FETs with a top-contacted configuration, showed a hole mobility of 0.13 cm 2 V −1 s −1 and on/off current ratio of 9.4 × 10 4. The device also showed large current of ca. 160 μA ( V D = −50 V; V G = −50 V), reflecting shorter channel length of the devices. We have evaluated self-assembled monolayer (SAM) through measurements of water contact angle and by Zisman plot. As a result, critical surface tension of the octadecyltrichlorosilane (OTS)-treated SiO 2 surface is 17 mN m −1 which is consistent with that of well-known SAM. We also well analyzed the cross-sections of the device by a scanning transmission electron microscopic (STEM) technique. The results indicated that the thicknesses of the pentacene layer in the channel part and Au layer in the source/drain part were ca. 30 and 30 nm, respectively. Furthermore, it is also indicated that the 100-nm grains of the pentacene were well adhered on the surface of the SAM-formed SiO 2 layer.

The synergistic effect of dope concentration and jetdrawing on structure development of wet-spun poly(acrylonitrile)

AbstractAcrylic fibers are the major precursor of carbon fibers. In this work, the synergistic effect of polymer concentration and jet stretching on porosity, morphology and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied and then the role of void size was elucidated. The results showed that the effect of jet stretching on fiber porosity is negligible below a threshold polymer concentration. Increasing polymer concentration up to 20 vol. % reduced the total porosity significantly but increased the nanometric void population slightly. On the other hand increasing polymer concentration and jet stretching simultaneously, improved mechanical properties as a result of a remarkable reduction in porosity. In addition, stretching shifted nanovoids distribution strongly toward smaller sizes. This was attributed to the effect of stretching and increasing polymer concentration on reducing the diffusion coefficient. Young's modulus of fibers also increased with decreasing overall porosity. Finally, strength-diameter correlation showed a good agreement with the Griffith's theory.

Micrometer-scaled Channel Lengths of Organic Field-effect Transistors Patterned by Using PEDOT/PSS Microfibers

Abstract We have easily fabricated channel patterns of organic field-effect transistors (OFET), in which channel lengths were ca. 5 μm, by using wet-spun poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) microfibers with diameters of ca. 5 μm. Pentacene-based OFETs with a bottom-contacted configuration, fabricated on the channel patterns, showed a hole mobility of 10−3 cm2 V−1 s−1 simply reflecting FET characteristics of the pentacene, and showed large current of 8 μA (VDS=−50 V; VG=−50 V) reflecting shorter channel length of the devices.

The influence of stretching on tensile strength and solubility of poly(vinyl alcohol) fibres

The strength of wet-spun poly(vinyl alcohol) ( pva) fibres is given as function of bath-stretching, wet-stretching and hot-stretching. In the two equations derived for strength of wet-stretching and hot-stretching the complex influence of the bath-stretching and hot-stretching is demonstrated. The bath-stretching is connected with a pure orientation effect and the residence time in the coagulating bath which is a measure for the ‘freshness’ of the fibre. The hot-stretching can be separated in a pure orientation effect and a crystallization effect. Fibres of the pva, used in the experiments, were soluble in boiling water. After shrinkage of the fibres at temperatures near the temperature of hot-stretching, the dissolution temperature can be raised. Insoluble pva fibres were prepared after removing most of the bulky residual ester groups.